The panels disclosed in this invention are panels having a double curvature, mainly located at the front of aircraft. These panels, generally made of a light alloy, have thicknesses ranging from 1 to 12 mm depending on the aircraft and the components of the panel (aluminum alloy, titanium alloy, metal composite or composite containing an organic resin).
If the material permits, the production of these panels requires shaping by drawing on a necessarily convex mold, while panels of composite material are shaped by draping-joining-infusion and compaction methods.
Because of its productivity and its flexibility, shaping by drawing is mainly employed.
This type of shaping is performed by means of a combination of traction on the panel and “envelopment” of the aforementioned convex mold so that the geometrically known shape of the panel (that which was in contact with the drawing mold) is the internal (concave) surface. The drawing process generates a plastic deformation of the overall thickness of the panel and consequently, through constriction, leads to a thinning of the section. Due to the non-deformable nature of the shape, this “loss of thickness” is not uniform over all surfaces of the panel.
The machining of such panels has alignment problems.
According to the art of alignment, the positioning of a solid is known as isostatic positioning when the 6 degrees of freedom it has in space (3 rotations and 3 translations along the axes of a tetrahedron) are held fixed by means of contacts with 6 judiciously positioned physical points. The isostatic positioning of a non-deformable panel is accomplished as shown in FIG. 1 of the drawings attached to the present description.